There are various press bending processes for forming bent glass sheets, particularly automotive glazings, wherein these processes function differently and which produce bent glass sheets of varying degrees of complexity of shape and of complexity associated with the types of bends.
Early press bending processes (see, for example, FIG. 1 that is similar to U.S. Pat. No. 4,043,782 to Bamford et al., which is incorporated herein by reference), typically include bending a heated glass sheet between a non-heated male mold and a female mold at relatively short cycle times. Upon being released from the male and female molds, the glazing is moved by way of transfer rollers to a subsequent step in the process, for example, glass quenching or annealing, which typically utilizes cooling gases.
Later press bending processes (see, for example, FIGS. 2-3 that are similar to U.S. Pat. No. 5,735,922 to Woodward et al., which is incorporated herein by reference), often include bending a heated glass sheet between a heated male mold and a ring-type female mold, wherein a vacuum may be drawn in holes and/or grooves (see, for example, U.S. Patent Application Publication No. 2005/0061034 to Boisselle et al. that is incorporated herein by reference), which are disposed through/on the male mold. Such vacuum is utilized to draw the heated glass sheet to a heated male mold shaping surface.
Subsequently, the vacuum is terminated when positive pressurized air is blown into the holes, in order to release a shaped glazing from the male mold. Upon being released from the male mold, the glazing is moved by way of a mechanical shuttle ring to a subsequent step in the process, for example, glass quenching (see, for example, FIGS. 2-3 and Woodward).
In comparison, the press bending processes like Bamford have, heretofore, been limited in the degree of complexity of shape and of complexity associated with the types of bends of which such processes are capable. On the other hand, the press bending processes like Woodward are capable of forming more complex bent glass sheets like windshields and some backlites. To their detriment, however, press bending processes, such as those disclosed in Woodward, require longer cycle times than press bending processes, such as those disclosed in Bamford, hence the processes, such as those disclosed in Woodward, typically result in higher manufacturing costs.
Recently, however, the automotive industry has increasingly been requiring more shape complexity and more complex types of bends for automotive glazings, while expecting improved optical quality, shape repeatability, and reduced finished product costs.
What is sought is a press bending process that reduces the cycle time (therefore, reducing the costs) necessary to produce automotive glazings with more complex types of bends, like windshields, sidelites, and backlites, similar to those formed in the press bending processes, such as those disclosed in Woodward, while exhibiting high optical quality and shape repeatability.